The LiftMaster K77-37857 is the gray operator cover used on the RSL12U family of residential slide gate operators. The cover is an important enclosure part because it shields the operator's electronics, battery area, wiring, and drive components from rain, dust, lawn sprinklers, insects, and sun exposure. A damaged cover may allow moisture into the operator or leave the unit looking unfinished and unsecured. This cover is specific to RSL12U / RSL12UL style slide gate operators and should not be swapped with RSW12U swing operator covers or larger commercial CSL/CSW covers. If the old cover color, lock area, or label layout differs, verify the part number by diagram before upload or ordering.
| Manufacturer | LiftMaster |
|---|---|
| Product Type | Gray operator cover |
| Part Number | K77-37857 |
| Application | RSL12U / RSL12UL cover replacement |
| Compatible Operator Type | Residential DC slide gate operator |
| Color / Finish | Gray |
| Included Components | Cover only unless current listing states otherwise |
| Notes | Also searched with K77-37855 in some listings |
RSL12U and RSW12U covers are easy to confuse by name, but one is for slide gate operators and the other is for swing gate operators. Always match the model tag before ordering.
For commercial gate operator repairs, verify the model, wiring, mechanical condition, and all required entrapment protection before returning the system to service.
K77-37857 is commonly listed for LiftMaster RSL12U and RSL12UL residential slide gate operators.
Yes. Public listings identify K77-37857 as a gray cover for RSL12U applications.
K77-37855 appears as an also-known-as or related cover reference in some listings. Verify by parts diagram before treating it as the same part.
No. RSW12U uses a different swing gate operator cover. RSL and RSW covers are not automatic substitutes.
Replace it when the original cover is cracked, missing, badly weathered, will not lock, or no longer protects the operator internals.